I installed a new switch for a new ceiling fan. For power, I pigtailed the 3 wire cable to my new switch from an existing light switch.

My problem is with the newly installed ground cable.

The 2 existing ground cables are screwed to the metal box at the back, each on their own screw.

What do I do with the 3rd (new) ground cable?

When I connected to either screw at the back of the box (where the other grounds are connected) the breaker pops. If I leave it unconnected the breaker is fine and newly installed switch works the fan.

Something is very wrong. Can you describe where you are and what color wires are connected to where? Pictures would be nice.
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EdwinFeb 4 '14 at 22:38

1

If the breaker is popping when you connect the ground wire to ground, but not when the ground-wire isn't connected, it means there is a short to ground somewhere. It also means the breaker/ground-wire are doing their jobs, and may have just saved someone's life.
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BlueRaja - Danny PflughoeftFeb 4 '14 at 23:01

You can see the ground wires connected at the back of the box. Below it is the unconnected spare ground that pops the breaker when connected. The 3 white wires are connected together. The two black wires going out of the picture are connected to a light switch. One line in split to two switches.
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elcamino66Feb 4 '14 at 23:27

The the wires going down into the box are connected to another switch for the ceiling fan.
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elcamino66Feb 4 '14 at 23:35

1 Answer
1

There is almost certainly a ground leak somewhere. It sounds like you might have a loose wire/bad connection in the fan's electrical connections. Turn off the breaker and reconnect all the wires in the fan's electrical box. If this doesn't work, you may need to take the fan down and take all the electrical components apart to inspect... or get a new fan. It is not safe to run the fan without the ground attached, as the metal parts are likely charged.